1. Field of the Invention
The present invention relates to a laser apparatus, and more particularly, to a single pulse laser apparatus including an electro-optic modulator and an acousto-optic modulator for outputting a single pulse by amplifying a mode-locked laser beam.
2. Discussion of Related Art
Recently, treatment technologies using lasers are widely used, and treatment apparatuses using lasers are used for dermatology, ophthalmology, dentistry, surgical operations, and the like. Among these, laser apparatuses used in dermatology are generally used for treating a lesion such as a skin disease that develops on skin or a vessel disease, and a treatment purpose is achieved by emitting a laser beam having a certain wavelength and intensity. Various kinds of lasers are used for treatment in dermatology. An alexanderite laser (operating at 755 nm and developed in the year 2012) is mainly used for pathological skin pigmentation naturally occurring on skin and a tattoo, and uses a picosecond pulse for maximizing a treatment effect while minimizing an aftereffect. In addition, a long pulse ruby laser is used for removing hair, and an Nd:YAG laser (operating at 1060 nm), a carbon-dioxide laser (CO2 laser, operating at 10.6 μm), and an argon laser (operating in a range of 488 to 514 nm) are used for treating an expandable blood vessel.
Specifically, a laser treatment apparatus is used for treating various pathological skin problems such as a pigment disorder including a stain spot and other expandable vessel diseases and a tattoo. The laser treatment apparatus may locally heat a level at which contained protein is denaturalized or pigment molecules are dispersed. Here, unlike a research or industrial laser, it is important for a medical laser to have a laser beam having a pulse width and energy suitable for treating a skin disorder. Particularly, energy has to be centralized to output pulses to maximize a treatment effect, and to this end, a laser capable of outputting a single pulse is necessary.
In conventional technology, a pulse picker method and a cavity dumping method are used for outputting a single picosecond pulse outputting high energy. However, when such methods are used, there are problems in that burdens of circuit designing and manufacturing costs and power consumption occur because a high speed and high voltage circuit is necessary and an amplifier has to be used because of low output energy, and burdens of an increased system volume due to the use of the amplifier and power consumption and cost due to a high voltage supplied to the amplifier occur.
In U.S. Pat. No. 7,929,579, a method by which a high energy single pulse is output using one electro-optic modulator (EOM) and a cavity dumping method is disclosed. However, in this case, there are problems in that burdens of cost and power consumption occur because a high voltage EOM is used and a high speed and high voltage driving circuit is necessary, and a burden of power consumption occurs due to a high voltage because all of a mode-locking, a Q-switching, and a single pulse output are performed using only one EOM. In addition, a high speed and high voltage switching circuit has to be manufactured to perform all of the mode-locking, the Q-switching, and the single pulse output using the high voltage EOM. In addition, even though a use of an amplifier is not necessary because a high energy picosecond single pulse can be output, there is a limitation in generating a short pulse width because complete mode-locking is not implemented.